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What is myIPaddress.com?
myIPaddress.com is a web site that automatically detects and displays your
computer's IP address. This can be helpful for configuring a computer on
a network, setting up communications software, or troubleshooting an Internet
connection. Your Internet Service Provider or IT help desk may ask you
to visit this site when you're having problems with your Internet connection.
What is an IP address?
Just as telephones are identified by unique telephone numbers,
computers on the Internet are identified by unique series of numbers called
"IP addresses". Each IP address consists of four numbers separated by
three periods; for example, "192.168.1.1". Whenever your computer talks
to another computer on the Internet -- such as when you visit a web site
-- the name of the other computer must be converted into an IP address
before communication can take place. (Incidentally, "IP" stands for
"Internet Protocol".)
Where do I get an IP address?
Most computers automatically get their IP addresses from the network;
that is, they are "dynamically assigned" by an Internet Service Provider
or IT department. The technologies that make this possible are
"DHCP" ("Dynamic Host Configuration Protocol") and "PPP" ("Point to
Point Protocol"). Fortunately, most modern operating systems handle
DHCP and PPP without much effort on the part of the user.
The only disadvantage of a dynamically-assigned IP address is that
it can change each time you connect to the Internet. (This can also
be viewed as an advantage, of course, as it makes it more difficult for
hackers to track you down.) If you are using software that requires
you to know your IP address, you may wish to visit myIPaddress.com whenever
you reconnect to the Internet.
If you have a continuous connection to the Internet, your Internet Service
Provider may assign you a "static IP address". A static IP address
identifies your computer on the Internet using the same address
as long as you remain with the same ISP. This is necessary if your
computer is to provide services on the Internet, such as e-mail or web hosting.
My IP address is wrong! How can that be?
If your computer is located behind a firewall, the firewall may be
hiding your computer's actual IP address from myIPaddress.com. In which
case the IP address displayed is actually the IP address of the firewall,
not your computer.
Similarly, if your computer is behind a "proxy server" or "web cache"
(i.e., a computer that intercepts requests for web pages in order
to speed up frequently-requested pages), the IP address displayed is
probably the IP address of the proxy server or web cache -- not your
computer.
Note that your computer may be behind a proxy server or web cache without your knowledge! A number of companies and Internet Service Providers use "transparent web caches", which intercept requests for web pages without any special configuration of your computer.
Is it okay to write a program that polls myIPaddress.com?
No. This site is not designed to be automatically polled by software. If you are writing a program that needs to detect your computer's IP address, you should use a web page that supports this type of activity, such as http://www.whatismyip.com/faq/automation.asp .
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